The GitHub blog has full details of how to set the authentication up, but, essentially, users can do it via SMS or a dedicated authentication mobile app — such as Google Authenticator (for Android/iPhone/BlackBerry), Duo Mobile (for Android/iPhone) or Authenticator (for Windows Phone 7).

The apps are important because GitHub admits that it isn’t able to send SMSes to users in every country worldwide, whereas the apps are available to all.

Like other solutions, GitHub’s two-factor authentication includes a ‘fallback’ SMS numbers and other systems for getting back into your account if you lose your phone.